US4779102A - Head drive system for a thermal printer - Google Patents
Head drive system for a thermal printer Download PDFInfo
- Publication number
- US4779102A US4779102A US06/937,014 US93701486A US4779102A US 4779102 A US4779102 A US 4779102A US 93701486 A US93701486 A US 93701486A US 4779102 A US4779102 A US 4779102A
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- US
- United States
- Prior art keywords
- heating elements
- level
- line
- data
- odd
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
- B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
- B41J2/35—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads providing current or voltage to the thermal head
- B41J2/355—Control circuits for heating-element selection
- B41J2/3551—Block driving
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
- B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
- B41J2/35—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads providing current or voltage to the thermal head
- B41J2/355—Control circuits for heating-element selection
- B41J2/3555—Historical control
Definitions
- the present invention relates to a thermal or a thermal transfer printer of the type using a line-type thermal head and, more particularly, to a head drive system associated with such a printer for printing out dots by multi-step modulation.
- Printers to which the present invention applicable include printers, facsimile terminals and copiers which are implemented with a line-type thermal head.
- a thermal printer or a thermal transfer printer uses a thermal head in which heating elements each being representative of a dot are arranged in one line in a main scanning direction. While a paper is fed by a stepping motor one line at a time in a subscanning direction, the thermal head is driven to generate heat in accordance with data to be recorded so as to print out data line by line.
- a problem with this type of thermal printer is that when a continuous string of dots are recorded, heat accumulated in the nearby heating elements effect each other to increase the density of dots printed out, resulting in an irregular density distribution as a whole.
- the mutual influence of dots which neighbor each other in the subscanning direction is not so serious because of the feed time of the paper, that of dots which neighbor in the main scanning direction is critical.
- the method begins with detecting the level data on a particular heating element to be driven and heating elements located at both sides of that particular heating element. Based on a weight for density compensation which corresponds to the level data, power applied to the particular heating element is controlled in terms of the duration of application or the peak value.
- This kind of method renders not only an apparatus for practicing the method but also the data processing complicated.
- a system for driving a thermal head which has heating elements arranged in one line in a main scanning direction of the present invention comprises a device for dividing the heating elements into an odd and an even dot groups with respect to one line of data to be recorded and driving the odd and even dot groups on a time division basis to generate heat, and a device for feeding a paper such that the odd dots and the even dots recorded on a same line are offset from each other in a subscanning direction.
- FIG. 1 shows dots which are printed out by a prior art head drive system
- FIG. 2 shows dots which may be printed out by a head drive system in accordance with one embodiment of the present invention
- FIG. 3 is a diagram showing a specific construction of a thermal head drive circuit
- FIG. 4 is a timing chart showing various signals which appear in the circuit of FIG. 3;
- FIGS. 5 and 6 show models of a recording
- FIG. 7 is a plot representative of a temperature distribution characteristic which is provided by driving odd dots and even dots of a thermal head on a time division basis;
- FIG. 8 shows a drive mode in accordance with another embodiment of the present invention together with a prior art drive mode
- FIG. 9 is a block diagram of an electric circuit
- FIG. 10 is a chart showing correspondence between neighboring dots and data conversion values
- FIG. 11 shows a relationship between the data conversion values and pulse widths
- FIG. 12 is a flowchart outlining the operation
- FIG. 13 is a flowchart demonstrating a particular transfer operation
- FIGS. 14A and 14B show exemplary solid picture which are recorded by the present invention and the prior art in a contrastive manner
- FIG. 15 is a block diagram showing an electric circuit in accordance with another embodiment of the present invention.
- FIG. 16 is a chart for explaining a data processing mode
- FIG. 17 is a chart showing a relationship between weights and pulse widths which are adapted to control heating elements
- FIG. 18 is a diagram for explaining the widths of pulses
- FIG. 19 is a table for explaining that the duration of a pulse applied to a heating element depends upon the level
- FIG. 20 is a flowchart outlining the operation of the entire arrangement.
- FIG. 21 is a flowchart demonstrating a particular transfer operation.
- a head drive system known in the art is such that heating elements are divided into an odd dot group and an even dot group and driven on a time division basis.
- this scheme may successfully preclude the mutual influence of heating elements which neighbor each other in the main scanning direction, it brings about another problem in relation to the representation of halftone. Specifically, as shown in FIG. 1, when dot modulation is preformed to change the size of dots to thereby render halftone, a blur a occurs between those dots D which have a usual area and those d which have a reduced area for rendering halftone and/or those dots D which are aligned in an oblique direction become spaced apart from each other as at b.
- a thermal head 10 includes heating elements H1 to H1280 which are arranged in a dot matrix and in one line in the main scanning direction X.
- the heating elements H1 to H1280 are divided into two blocks, i.e. a former block and a latter block.
- One line of data DATA to be recorded which are fed serially to the drive circuit are held by a latch 14 via a shift register 12.
- the heating elements H1 to H640 in the former block of the head 10 are driven by a driver 16 according to the data being held by the latch 14.
- the heating elements H641 to H1280 are driven by the driver 16 according to the data being held by the latch 14.
- a latch signal is represented by LATCH in the drawing.
- one line of data DATA are divided into data associated with an odd dot group and those associated with an even dot group.
- the resulting odd data (non-printing or dummy data being inserted in even data portions) ODD-DATA and even data (non-printing or dummy data being inserted in odd data portions) EVEN-DATA are fed to the shift register 12 sequentially.
- the stepping amount of a stepping motor adapted to feed a paper in the subscanning direction Y is equal to 1/4 of a dot having an ordinary size, so that the head 10 may become aligned with the next line on a paper when the paper has been fed four steps in total.
- one line of odd data ODD-DATA are fed and, then, only odd ones of the heating elements H1 to H640 which belong to the former block of the head 10 are driven by a strobe STB1 according to the data so as to generate heat.
- This is followed by applying a one-step pulse to the stepping motor to feed a paper by 1/4 dot in the subscanning direction.
- only odd ones of the heating elements H641 to H1280 which belong to the latter block are driven by a strobe STB2 according to the data so as to generate heat.
- a one-step pulse is applied to the stepping motor to feed the paper by another 1/4 dot in the subscanning direction, whereafter the even ones of the heating elements H1 to H640 of the head 10 are driven by another strobe STB1 according to the data.
- a one-step pulse is applied to the stepping motor to feed the papar farther by 1/4 dot in the subscanning direction, whereafter the odd ones of the heating elements H641 to H1280 of the head 10 are driven by another strobe STB2 according to the data.
- a one-step pulse is applied to the stepping motor to feed the paper farther by 1/4 dot in the subscanning direction, thereby completing one line of recording.
- FIG. 4 shows a relationship between the various signals which appear in the drive circuit as described above.
- SP designates the step pulses which are fed to the stepping motor.
- FIGS. 5 and 6 there are shown data models which are recorded by the above procedure.
- y1 is representative of an offset by 1/2 dot
- y2 an offset by 1/4 dot
- O the center position between the former and latter blocks of the head 10.
- the distribution of temperature which is generated in the individual heating elements of the heat 10 is shown. If the even heating element H2 is driven immediately after the odd heating elements H1 and H3 have been driven, the temperature of the element H2 being driven will be elevated beyond a predetermined level L, as indicated by a dotted line, under the influence of heat which is accumulated in the elements H1 and H3. In accordance with this embodiment of the present invention, after the odd heating elements H1 and H3 have been driven, the paper is fed by 1/4 dot and, then, the even heating element H2 is driven.
- Another advantage attainable with this embodiment is that noise generated by the stepping motor is reduced since the intervals of the step pulses SP for driving the stepping motor are uniform. Applying four step pulses at a time to a stepping motor every time one line of recording is completed, as has heretofore been practiced, would cause the motor to be driven in an intermittent fashion to generate much noise, and such highspeed drive would be heavy in view of motor torque.
- a head drive system for a thermal printer in accordance with this embodiment is capable of recording a picture of good quality without encountering an irregular density distribution or without causing a blur and a gap between dots printed out.
- This advantage is derived from the fact that heating elements of the head are divided into an odd and an even dot groups and driven on a time-division basis, and that one line of data are recorded such that odd dots and even dots which neighbor each other in the main scanning direction are offset from each other in the subscanning direction.
- this embodiment is such that heating elements of a thermal head are divided into an odd and an even dot groups, and the odd elements are driven before the even elements. Stated another way, odd dots are transferred after even dots. Further, weights 0, 1, 2 and 3 are used as drive levels. Let the heating element of level 0 be the element S0, the element of level 1 be the element S1, the element of level 2 be the element S2, and the element of level 3 be the element S3. Then, in this particular embodiment, the odd elements are driven under the following three different conditions:
- the drive mode as stated above is shown together with a prior art drive mode for comparison purpose.
- the even element at a point X1 falls under the condition (1) as mentioned above, and the even element at a point X2 falls under the condition (2).
- these particular elements are driven simultaneously with the odd group.
- an electric circuit for implementing such a manner of drive is shown in a block diagram.
- one line of picture data fed from a host machine are applied to an M line buffer 20 to be stored therein and, at the same time, to a dot detector 22 which serves to determine presence/absence of a dot.
- a line shift register 24 latches a ONE when a dot is present as determined by the dot detector 22, and a ZERO when a dot is absent.
- the data latched by the line shift register 24 are transferred to an S line buffer 26 when the next one line of data are entered.
- the one line of picture data stored in the M line buffer 20 as stated above are separated into odd data and even data by a data separator 28 in response to an odd/even state signal, the odd and even data being routed to a shift register 32 which is included in a decision section 30.
- the data (C) stored in the line buffer 26, i.e., ONEs and ZEROs which are representative of presence/absence of dots on one line are fed to a register 34 of the decision section 30 sequentially.
- the decision section 30 determines whether both of dots A and B which are located at both sides of a particular odd element, or observed dot, X are of level 3 or at least one of them is of level 3, and whether or not a dot was present in the dot data C corresponding to the observed odd element which appeared one line before.
- the contents decided by the decision section 30 are each weighted according to a data conversion ROM 36 and, thereby, converted to a particular value Y as shown in FIG. 10.
- the value Y is further converted by a pulse width converter 38 to an electric signal whose pulse width is associated with the particular value Y, as shown in FIG. 11.
- the electric signal is fed to a thermal head to transfer the data.
- the system in accordance with this embodiment is constructed to, when the elements which neighbor a certain element are of maximum drive level, drive them at the same time.
- Experiments showed that while the prior art system has to assign 2 msec to each dot to record a solid picture as shown in FIG. 14A, in accordance with this embodiment 1.4 msec per dot is sufficient in recording a solid picture as shown in FIG. 14B.
- this embodiment requires a minimum of total energy since it is capable of recording a solid picture with small energy without affecting the reproducibility of halftone levels, which is a merit particular to the odd/even separation type drive system.
- FIG. 15 shows an electric circuit for practicing this embodiment in a block diagram.
- one line of picture data fed from a host machine are separated into the levels 1, 2 and 3 by a data separator and zero detector 40, whereby for each of the levels a ONE is produced when the level data is present and a ZERO when it is absent.
- the binary codes, ONEs and ZEROs, which are associated with each level are stored in one of level buffers 42 (1), 42 (2) and 42 (3) assigned therewith.
- a dot detector 44 on the other hand, produces a ONE when the level of data is 1, 2 or 3 and a ZERO when it is 0.
- the outputs of the dot detector 44 are stored in a current line buffer 46 and, upon entry of data on the next line, transferred to a previous line buffer 48.
- FIG. 16 shows the weights of picture data entered, the levels separated by the data separator 40 based on those weights, the weights of picture data appeared on the previous line, and the outputs of the dot detector 44 which correspond to the weights of the image data appeared on the previous line.
- each of the level buffers 42 (1), 42 (2) and 42 (3) are sequentially fed to a shift register 52 of a comparing section 50 while, at the same time, the contents of the previous line buffer 48 are sequentially fed to a register 54 of the comparing section 50.
- An encoder 56 which is associated with the comparing section 50 weights on a level-by-level basis the data stored in the shift registers 52 and 54 by referencing the binary codes assigned to the elements A and B next to the observed element X and a code which shows whether or not a dot was present in the dot data C on the observed element which appeared one line before. The weights are shown in the left column of FIG. 17.
- a pulse width converter 58 converts the weights to pulses whose widths correspond to the weights on a level-by-level basis, the pulses being applied to the individual heating elements in the order of the levels 1, 2 and 3.
- the reference times Ta, Tb, Tc and Td differ from one level to another such as shown in FIG. 19.
- FIG. 20 shows the outline of the procedure as described above, while FIG. 21 shows a particular transfer operation which is performed level by level.
- those heating elements which are of the same level are driven at the same time. This enhances reproducibility of the area and density of a dot of each level and simplifies the apparatus construction as well as data processing.
- a quality recording which is free from irregular density is achieved since a weight is determined by referencing dot presence/absence data on a particular heating element which appeared one line before and level data on two heating elements next to that element and the width of a pulse to be applied to that particular element is adjusted based on the weight.
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Abstract
Description
Claims (8)
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP60274076A JPH0683336B2 (en) | 1985-12-05 | 1985-12-05 | Thermal head drive system |
JP60-274076 | 1985-12-05 | ||
JP60274075A JPH07112228B2 (en) | 1985-12-05 | 1985-12-05 | Thermal head drive method |
JP60-274075 | 1985-12-05 | ||
JP61007023A JPS62165474A (en) | 1986-01-16 | 1986-01-16 | Thermal printer driving control system |
JP61-7023 | 1986-01-16 |
Publications (1)
Publication Number | Publication Date |
---|---|
US4779102A true US4779102A (en) | 1988-10-18 |
Family
ID=27277443
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/937,014 Expired - Lifetime US4779102A (en) | 1985-12-05 | 1986-12-02 | Head drive system for a thermal printer |
Country Status (1)
Country | Link |
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US (1) | US4779102A (en) |
Cited By (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0401820A2 (en) * | 1989-06-08 | 1990-12-12 | Mitsubishi Denki Kabushiki Kaisha | Recording density correction apparatus in printer |
US5075701A (en) * | 1990-07-17 | 1991-12-24 | Matsushita Electric Industrial Co., Ltd. | Thermal recording head having group-wise actuable heating elements |
US5138337A (en) * | 1990-05-10 | 1992-08-11 | Eastman Kodak Company | Apparatus for grey level printing using a binary architectured printhead |
US5142296A (en) * | 1990-11-09 | 1992-08-25 | Dataproducts Corporation | Ink jet nozzle crosstalk suppression |
US5196864A (en) * | 1991-08-12 | 1993-03-23 | Eastman Kodak Company | Electronic registration in a multiple printhead thermal printer |
US5255013A (en) * | 1990-11-07 | 1993-10-19 | Eastman Kodak Company | Multiple address grey level LED printing with binary architectured printhead |
US5297878A (en) * | 1990-05-15 | 1994-03-29 | Fuji Photo Film Co., Ltd. | Method of thermal wax transfer printing |
US5349623A (en) * | 1991-10-14 | 1994-09-20 | Mitsubishi Denki Kabushiki Kaisha | Driving circuit for exothermic resistors |
US5355793A (en) * | 1991-08-21 | 1994-10-18 | Fuji Photo Film Co., Ltd. | Method and apparatus for making a mimeographic printing plate |
US5519426A (en) * | 1993-11-01 | 1996-05-21 | Lasermaster Corporation | Method for controlling a thermal printer to increase resolution |
US5907666A (en) * | 1994-11-17 | 1999-05-25 | Canon Kabushiki Kaisha | Recording system for transferring offset data to be recorded |
US6031554A (en) * | 1995-03-14 | 2000-02-29 | Mitsubishi Denki Kabushiki Kaisha | Halftone recording method and apparatus |
US6211893B1 (en) * | 1998-09-09 | 2001-04-03 | Fujicopian Co., Ltd. | Multi-gradation recording method |
US6567111B2 (en) * | 2000-11-22 | 2003-05-20 | Fuji Photo Film Co., Ltd. | Image recording method and apparatus |
US20080302259A1 (en) * | 2007-06-05 | 2008-12-11 | Tohoku Ricoh Co., Ltd. | Stencil printing apparatus |
KR20200007700A (en) * | 2018-07-13 | 2020-01-22 | 캐논 가부시끼가이샤 | Printing apparatus, printing method, and storage medium |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4141018A (en) * | 1976-11-08 | 1979-02-20 | Tokyo Shibaura Electric Co., Ltd. | Thermal recording head and drive circuit |
US4531133A (en) * | 1983-02-02 | 1985-07-23 | Fuji Xerox Co., Ltd. | Thermal recording device |
US4560988A (en) * | 1981-07-17 | 1985-12-24 | Fuji Xerox Co., Ltd. | Thermal head driving method |
-
1986
- 1986-12-02 US US06/937,014 patent/US4779102A/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4141018A (en) * | 1976-11-08 | 1979-02-20 | Tokyo Shibaura Electric Co., Ltd. | Thermal recording head and drive circuit |
US4560988A (en) * | 1981-07-17 | 1985-12-24 | Fuji Xerox Co., Ltd. | Thermal head driving method |
US4531133A (en) * | 1983-02-02 | 1985-07-23 | Fuji Xerox Co., Ltd. | Thermal recording device |
Cited By (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0401820A2 (en) * | 1989-06-08 | 1990-12-12 | Mitsubishi Denki Kabushiki Kaisha | Recording density correction apparatus in printer |
EP0401820A3 (en) * | 1989-06-08 | 1991-05-15 | Mitsubishi Denki Kabushiki Kaisha | Recording density correction apparatus in printer |
US5166701A (en) * | 1989-06-08 | 1992-11-24 | Mitsubishi Denki K.K. | Recording density correction apparatus in printer |
US5138337A (en) * | 1990-05-10 | 1992-08-11 | Eastman Kodak Company | Apparatus for grey level printing using a binary architectured printhead |
US5297878A (en) * | 1990-05-15 | 1994-03-29 | Fuji Photo Film Co., Ltd. | Method of thermal wax transfer printing |
US5075701A (en) * | 1990-07-17 | 1991-12-24 | Matsushita Electric Industrial Co., Ltd. | Thermal recording head having group-wise actuable heating elements |
US5255013A (en) * | 1990-11-07 | 1993-10-19 | Eastman Kodak Company | Multiple address grey level LED printing with binary architectured printhead |
US5142296A (en) * | 1990-11-09 | 1992-08-25 | Dataproducts Corporation | Ink jet nozzle crosstalk suppression |
US5196864A (en) * | 1991-08-12 | 1993-03-23 | Eastman Kodak Company | Electronic registration in a multiple printhead thermal printer |
US5355793A (en) * | 1991-08-21 | 1994-10-18 | Fuji Photo Film Co., Ltd. | Method and apparatus for making a mimeographic printing plate |
US5349623A (en) * | 1991-10-14 | 1994-09-20 | Mitsubishi Denki Kabushiki Kaisha | Driving circuit for exothermic resistors |
US5519426A (en) * | 1993-11-01 | 1996-05-21 | Lasermaster Corporation | Method for controlling a thermal printer to increase resolution |
US5661514A (en) * | 1993-11-01 | 1997-08-26 | Lasermaster Corporation | Method and apparatus for controlling a thermal print head |
US5907666A (en) * | 1994-11-17 | 1999-05-25 | Canon Kabushiki Kaisha | Recording system for transferring offset data to be recorded |
US6031554A (en) * | 1995-03-14 | 2000-02-29 | Mitsubishi Denki Kabushiki Kaisha | Halftone recording method and apparatus |
US6211893B1 (en) * | 1998-09-09 | 2001-04-03 | Fujicopian Co., Ltd. | Multi-gradation recording method |
US6567111B2 (en) * | 2000-11-22 | 2003-05-20 | Fuji Photo Film Co., Ltd. | Image recording method and apparatus |
US20080302259A1 (en) * | 2007-06-05 | 2008-12-11 | Tohoku Ricoh Co., Ltd. | Stencil printing apparatus |
US7878117B2 (en) * | 2007-06-05 | 2011-02-01 | Tohoku Ricoh Co., Ltd. | Stencil printing apparatus having controlled thermal head for perforating stencil |
KR20200007700A (en) * | 2018-07-13 | 2020-01-22 | 캐논 가부시끼가이샤 | Printing apparatus, printing method, and storage medium |
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